US3304882A - Cryoliquid pump - Google Patents

Description

Feb. 21, 1967 J R T 3,304,882

' RYOLIQUID PUMP Filed June 5, 1964 3 Sheets-Sheet 2 NVENTOR JAMES D. YEAROUT United States Patent 3,304,882 CRYOLIQUID PUMP James D. Yearout, Waynesboro, Va., assignor to The La Fleur Corporation, Los Angeles, Calif., a corporation of California Filed June 5, 1964, Ser. No. 372,747 6 Claims. (Cl. 103-153) The present invention relates to a reciprocating multiple piston pump adapted to be secured to the wall of a container of liquid so as to have its pump cylinders and pistons inside the container and immersed in the liquid to be pumped, and to have the pump rods extend out of such liquid and such container for connection to their actuators; the liquid to be pumped being such as nitrogen, oxygen, helium, or hydrogen under low pressure and at very low temperature, and such liquid to be pumped against either low or high heads. Such liquids may be called cryoliquids.

Pump construction of this kind and for this purpose has had the problems of inlet pressure drops causing the formation of gas in the pump cylinders, and much trouble, due to frosting, in maintaining a gas and liquid seal along pump rods where they leave the container, the zone of transition from the low temperature of the liquid to the ambient temperature surrounding the container. Also, it has been a problem in duplex pumps to maintain the two pistons in step and in full stroke. Reliability and simplicity are of prime importance in pumping such liquids as pump failures may result in serious losses of liquid, and in damage to other equipment. 7

For the above reasons, it is an object of the present invention to devise a pump for loW temperature liquids that has inlet checks and passageways that oifer negligible resistance to liquid flow.

Another object of the invention is the devising of a pump shaft heating means and insulating construction that prevents the formation of frost on the shaft, its bearings, and its seals so that the bearings and seals will have a long operational life.

A further object of the invention is the construction of a synchronizing linkage for a duplex pump that insures the pumps staying in step and at full stroke. It is, also, an object to apply such synchronizing means to a hydraulic drive for such duplex pump.

The above mentioned defects of the priorart are remedied and these objects achieved by a reciprocating piston pump construction having a mounting flange about midway of the length of the pump assembly that is securable to the inner wall of an insulated container, or vessel, so that it surrounds an opening in such wall located adjacent the bottom of the tank, with the pump pistons and cylinders inside of the wall and portions of the pump rods and the pump actuators outside of the wall with partitions and seals along the shafts to prevent the leakage of liquid or gas along such rods.

Intake head loss is reduced to a negligible amount by making the intake opening of substantially'the same area as the piston area, and by the use of an inlet check valve that moves aside and away from its seat to leave the opening free for liquid flow, and by the inlet passage being short and in direct communication with the body' of liquid in the container.

Frosting along the pump rods is prevented by the rods being long enough to extend from the inside of the container to well outside thereof to provide a heated isolating length of and for each rod. This isolating length is heated by the circulation of gas from .such liquid in a chamber around a rod and along such insulating length. This circulation is effected by an annular piston secured to such length, such piston reciprocating in such chamber to surge the gas thru a heating coil external of the chamber.

The pump is provided with one double acting piston for use in pumping against low heads, and two single acting pistons of relatively small diameter with respect to the single low head piston, for use in pumping against high heads. The three pistons and their cylinders, and'their piston rods are contained in a single housing. A separate hydraulic drive cylinder is associated with each of the piston rods, and the two high pressure pump rods are provided with cross connected linkages that control the admission of drive fluid to the drive cylinders so that the high pressure pistons stay in step and so that each one has maximum stroke. The arrangement of the two high pressure pumps and their actuating cylinders, and their control linkage is similar to that of many duplex pumps. Each pump rod is provided with a control cam that contacts a cam follower as it reaches each end of its stroke. The cam followers associated with each cam are secured at opposite ends of a rocker, and two adjacent ends of the rockers are linked to opposite ends of a floating lever that is midconnected to a control valve, or pilot valve, for a main hydraulic valve. With this arrangement, the control valve is never in either of its extreme positions until both pump rods have moved to their extreme positions. Thus, the flow of motive fluid is not reversed until both piston rods have reached the ends of their strokes.

The cryoliquid pump construction briefly outlined above is hereinafter described in detail and illustrated in the accompanying drawings, in which:

FIGURE 1 is a cabinet view of the pump assembly.

FIGURE 2 is an isometric view of a portion of the pump base showing one of the high pressure pumps in quarter section with the pump rod broken away.

FIGURE 3 is an isometric view in quarter section of a shaft heater unit with the pump rod broken away on both sides of the unit.

FIGURE 4 is a schematic line drawing of the entire pump assembly and the controls therefor.

The pump assembly is shown in a physiml embodiment illustrated in the cabinet drawing of FIGURE 1, and is diagrammed in the schematic line drawing of FIGURE 4. The following description refers to both of these figures. The complete assembly is a unit that may, for the purpose of consideration and description, be divided into four sections: pump, heater, control, and drive. The pump section is placed inside of and adjacent the bot-tom of a tank that contains the cryoliquid to be pumped. The rest of the assembly is outside of the tank. S-uch tank is not shown. The assembly is secured to a tank wall and in an opening therein that is of a size and shape to fit inwardly of a pump mounting flange 11. The tank flange 11 has a circle of bolt holes 12 that align with bolt holes in the tank so that bol-ts thru the aligned holes may secure-the assembly to the tank wall with the section to the right, in the figures, of the flange, the pump section, inside of the tank. The flange extends across the pump to seal the tank opening except for packed openings in the flange for the output piping of the pump and the pump rods. A double acting piston 13 is housed in a cylinder 14. This piston is intended for pumping against low heads, and is of relatively large diameter as compared with two other pistons 15, 16 located below and parallel to the low pressure piston and cylinder. These pistons are intended for use in pumping against much higher heads than those against which the large piston operates. The cylinders 17, 18 for the high pressure pistons are part of a base 19 to which the low pressure cylinder 14 is bolted. The low pressure. cylinder has .a cap 21 that has formed therein an inlet" opening having an inlet check 22 and an opening for an outlet check 23. The base 19 is similarly provided with.

a low pressure inlet and check 24 and a low pressure outlet check 25. Each of the high pressure cylinders has an inlet check 27, 28 and an outlet check 29, 30. The base 19 is spaced from and connected to the mounting flange 11 by a frame that is concealed by a cover 31, and this space is used to insulate the pumps from the tank wall.

To the left of the mounting flange 11 are a pump rod heater section and a pump control section, both in a housing delineated n FIGURE 1 by a series of ribs 32 that extend parallel to the pump rods 33, 34, 35, of the pistons, and which ribs are joined together to form a cylindrical housing for the shaft heaters and the pump controls. The right hand end of the heater housing is secured to the tank flange 11 and the other end, the outer end, is closed except for the pump rod and piping openings therethru, and the outer end serves as a base for the hydraulic cylinders 36, 37, 38, one for each pump rod, that operate the pumps. Mounted on and exteriorly of the heater section 32 are three heat exchangers 39, 40, 41. A junction box 42 for the outlet piping of the pumps is located on the near side of FIGURE 1, the piping is not shown; and a similar box on the far side accommodates the control piping for the hydraulic cylinders. The outlet pipe 43 for the near side high pressure piston is partially shown as are the outlet pipes 44, 45 for the two ends of the low pressure piston. The outlet pipe for the far side low pressure piston i concealed by the view. All of these outlet pipes pass thru the mounting flange 11 interiorly of its bolt hole circle but such has not been illustrated.

All of the inlet check valves 22, 24, 27, 28 are of the same construction and size, and only one valve 28 in the inlet port of one of the high pressure pump cylinders 18 will be described, as illustrated in FIGURE 2 in the quarter section isometric view of a portion of the base 19 from the back side of FIGURE 1. The check disc 51 that closes the port is pivoted to the inner end of a U-shaped check arm 52 that has its outer end pivoted in a slot in a flange 53 integral with one end of a sleeve 54 whose other end acts as the seat for the check disc 51. The flange 53 is bolted and sealed to the face of the base 19. The bore of the sleeve 54 forms the pump inlet, and the sleeve'is coaxial of the cylinder 18 and the piston 16 therein. The construction and operation of the check is such that as the piston moves from the check, liquid flows inward thru the port to move the disc off its seat. The U-shaped arm pivots in the flange asymmetrically of the sleeves axis, and its disc end moves inward of the cylinder and upward until it contacts the sleeve wall. The cylinder arjacent the seat is annularly relieved so that a part of the disc may move upwardly into this relieved area 56, and the lower portion of the disc may swing inwardly, movement in two degrees of freedom. The inward and upward movement of the check disc is sufficient, with the annular relief 56, to allow fluid flow with negliga'ble head. The outlet check 30 is not shown in detail but is placed in the outlet passage 57 that leads to an outlet pipe such as the near side one 43 shown in FIGURE 1.

FIGURE 3 is an isometric view of a pump rod bearing and heater assembly, in quarter section, such as is associated with each of the three rods of the pump. The view is from the back side of FIGURE 1. The assembly is provided with a bolt-ring mounting flange 61 that is bolted to the left side of the pump mounting flange 11, and thru which one of the pump rods, 35 for example, extends, a portion only of the rod being shown in this view. Secured to the flange 61 is a cylindrical sleeve 63 having a series of spaced apart annular fins 64 integral with the exterior thereof. The inner surface of the sleeve is spaced from the pump rod to form an annular bore between rod and sleeve. A sleeve bearing 66 is secured in the left hand end, in FIGURE 3, of the sleeve for the support of the rod and to seal the left end of the bore. The right end of the bore is sealed by a packing ring 67. The rod carries a piston ring 68, and this piston ring is so placed that in the normal travel of the rod the ring reciprocates, substantially, from end to end of the bore. Also, the piston ring is of a thickness to create a sliding seal between the rod and the inside of the sleeve. Thus, as the piston ring reciprocates in the bore it acts to pump any gas or liquid therein. The opposite ends of the bore are in communication thru a coil formed by a tube 69, and the pumping action of the piston ring 68 forces such gas or liquid to oscillate or surge in the coil 69. Heat from an external source is applied to the coil 69. The purpose of this construction is such that any of the liquid being pumped that leaks past the sleeve bearing 66 is either vaporized by being pumped into the hot coil 69, is vaporized by the warmed surfaces in the bore, or is vaporized by the warm gas in the bore. Thus, there is no frosting of the pump rod 35, the bearing 66, the packing ring 67, or the piston ring 68 as would occur if heat were not applied to these parts and the liquid were to cool such parts by evaporation, and further liquid were to solidify on such parts due to such evaporative cooling. Such frosting would score the bearing, and wear and break the packing 67. Each of the heating coils 69 is contained in one of the heat exchangers 39, 40, 41 shown in FIGURE 1. Heat is also received by the sleeve 63 from the fins 64 attached thereto that receive ambient heat, and this ambient heat helps to prevent frosting at such time as the pump is not in operation but the pump is submerged in a cryoliquid.

The operation and linkages of the pump drive controls are illustrated by the schematic showing of FIGURE 4, rather than by views of the actual mechanisms. The controls are illustrated in the so labeled control section of FIGURE 4, and are found in the left hand portion of the cover 31 of FIGURE 1. The two high pressure ump rods 34, 35 are in effect cross linked so that they stay in step, one with respect to the other. The low pressure pump rod 33 is independent of the other rods in its operation. Each of the rods is driven by a double acting hydraulic power cylinder 36, 37, 38, and these power cylinders are controlled by various hydraulic valves actuated from cams secured to the pump rods.

The operation of the low pressure rod 33 control wilt be described first as it is the simpler of the two controls. An annular shaped cam 71, illustrated as a ball, is secured coaxially of the pump rod 33. The annular shape allows the cam to contact its followers regardless of the rotation of the rod. Adjacent the rod is a follower rocker 72 that has a pivot 73 medically of two followers 74, 75. The rocker and its followers are so shaped and placed that each follower is contacted in turn by the rod cam as the rod reaches first one and then the other limit of its stroke. This alternate contacting of the followers causes the rocker ends to swing. To one end of the rocker 72 there is pivotally connected one end of a link 77 whose other end is pin connected to the spool 05 a hydraulic pilot valve 78 so as to actuate said valve in unison with the actuation of said rocker. This pilot valve is hydraulically connected by lies 79, 80 with a master valve 82 that controls the admission and discharge of pressurized hydraulic fluid thru the lines 83, 84, alter-- nately, to opposite ends of the hydraulic drive cylinder 36 and to oposite sides of the piston 86 therein to effect reciprocation of such piston and its connected rod 33. The distance between the cam followers 74, along the pump rod 33 determines the length of stroke of the rod and the travel of both the drive piston 86 and the pump piston 13, as well as the heater piston ring 68. The speed of pumping will, largely, be determined by the pressure of the hydraulic drive fluid delivered to the drive cylinder 36 by the hydraulic control system.

The high pressure cryoliquid pumping pistons 15, 1.6 are controlled so that their movement with respect to each other is sensed in opposite directions and they reverse directional sense together. The high pressure pump rods 34, 35 are parallel to the low pressure rod 33, and all three hydraulic actuating cylinders are parallel and in opposition,

mounted in the same general location, the drive section. As illustrated in FIGURE 4, one of the drive pistons 91 is approaching the left hand end, the front end, of its cylinder, and the other piston 92 is approaching the back end of its cylinder, the right hand end. Each of the pump rods 34, 35 is provided at the control section with an annular cam 93, 94- concentric of the rod. Parallel to each rod is a pivoted follower rocker 95, 96 having thereon followers 97, 98, 99, 100. This above construction and operation of cams, and followers is the same as for the low pressure control. As shown in FIGURE 4, the right hand end of each of the follower rockers 95, 96 is pivotally connected to one end of separate links 101, 102. The other end of one link 101 is pivotally connected to one end of a floating lever 103 and the other end of the other link 102 is pivotally connected to the other end of the floating lever 103. The midportion of the floating lever is linked 104 to the spool of a hydraulic pilot valve 105 for actuation thereof. The pilot valve 105 is hydraulically connected by lines 106, 107 to a master valve 108 that controls the admission and discharge of pressurized hydraulic fluid alternately thru the lines 109, 110 to the front end of one and the other of the drive cylinders 37, 38 and against the front side of one and the other of the pistons 91, 92 to effect travel thereof toward the back ends of their cylinders, and to effect pumping of the cryoliquid. The two cylinders are hydraulically cross connected adjacent their back ends. This hydraulic cross connection 111 effects the return of the pistons to the head ends of the cylinders, one piston driving the other in the opposite direction by means of this cross connection 111. The cross linking of the controls for the two high pressure pump rods has two purposes: first, it keeps the rods in step, and second, if fluid leaks from the cross connected back ends of the cylinders, each hydraulic piston will lag in reaching the head end of its stroke until the other piston at the back end of its stroke has leaked fluid to compensate for the lost cross connecting fluid.

With this construction, by the use of the floating lever 103, the midpoint of the floating lever has a path of travel along with the spool of the pilot, and each end of the floating lever has a separate path of travel. Each path has two extremes, the opposite ends of the path. Each end of the floating lever moves from one end to the other of its path upon a swing of its related follower rocker, but the midpoint of the floating lever is not moved to an extreme position of its path until both ends of the lever have moved in the same directional sense. Thus, if one of the pump rods reaches its end of travel before the other one, the pilot spool is partially moved to reverse but not enough to cause reversal of the pump rod travel. Reversal does not occur until the other rod and the other end of the floating lever reach their extreme positions.

While the two high pressure drive cylinders are shown hydraulically connected in series by the cros connection line 111, the disclosed control linkages and hydraulic controls could be used with the drive cylinders hydraulically connected in parallel or with the drive pistons being returned by spring means. Further, such construction are not dependent on the pumps being single or double acting, or dependent on the two high pressure pump rod moving with the opposite directional sense. The important aspect is that the control linkage provides a means of insuring that both rods must reach their extreme positions before the controls reverse the directional sense of the rod travel.

The disclosed device may be used for pumping cryoliquids against low or high heads. The pump cylinders are immersed in the liquid to be pumped so that vaporization and cavitation is eliminated or negligible. The inlet check valves are of large area and offer negligible resistance to flow to reduce further the possibility of vaporization and cavitation. Simple and effective means are provided for heating the pump rod bearings and seals to eliminate frosting thereof. The control and drive mechanisms are simple and effective. Bearings, seals, controls, and drive are located so as to be outside of the liquid tank and easily accessible for servicing.

Having thus described my invention, its construction and operation, I claim:

1. A shaft warmer for a shaft movable axially thereof, comprising: a round shaft, a sleeve coaxial of and spaced from said shaft so that said shaft and sleeve form therebetween an annular bore, means sealing the ends of said bore to allow for axial reciprocal movement of said shaft in said sleeve, a piston ring carried by said shaft in said sleeve and sealing said bore between said shaft and said sleeve, and a conduit connecting the opposite ends of said bore and having a portion extending externally of said sleeve whereby the fluid in said bore moves from one end to the other as said shaft moves axially.

2. The combination of claim 1 including means for applying heat to said conduit portion.

.3. A cryoliquid pump having an axially movable primary impeller for said liquid, a shaft carrying and driving said impeller, a housing for said impeller and said shaft with said shaft extending externally thereof, said housing forming an axially extending bore around and spaced from said shaft, spaced apart means sealing the ends of said bore, a conduit external of said housing and having its opposite ends in spaced apart communication with said bore, and a secondary impeller carried by said shaft in said bore for circulating fluid thru said conduit to the opposite ends of said bore as said shaft moves axially.

4. The combination of claim 3 including means for applying heat to said conduit.

5. The combination of claim 3 including: a tank wall mounting flange secured peripherally of and to said housing between said impellers.

6. In a cryoliquid pump, a housing, a shaft'in said housing, spaced apart shaft seals forming an enclosed space between said shaft and said housing, and permitting axial movement of said shaft, conduit means in communication with and external of said space for allowing free circulation of gas to and from said space through said conduit as said shaft moves axially, and means mounted on said shaft intermediate said shaft seals for inducing such circulation.

References Cited by the Examiner UNITED STATES PATENTS 262,119 8/1882 Reynolds 103-49 695,989 3/ 1902 Worthington 103-49 2,507,895 5/1950 Foxtow 277-22 2,851,860 9/1958 Lindsey 60-97 3,117,792 1/1964 Glenn et a1. 277-22 3,144,045 8/1964 Fitzpatrick 137-527.8 3,144,876 8/1964 Frye 137-527.8 3,154,925 11/1964 De Vita 60-97 3,216,651 11/1965 King et a1. 230-203 FOREIGN PATENTS 138,708 1/1953 Sweden.

57,132 7/ 1911 Switzerland.

DONLEY I. STOCKING, Primary Examiner. HENRY F. RADUAZO, Examiner.

Claims (1)

1. 3. CRYOLIQUID PUMP HAVING AN AXIALLY MOVABLE PRIMARY IMPELLER FOR SAID LIQUID, A SHAFT CARRYING AND DRIVING SAID IMPELLER, A HOUSING FOR SAID IMPELLER AND SAID SHAFT WITH SAID SHAFT EXTENDING EXTERNALLY THEREOF, SAID HOUSING FORMING AN AXIALLY EXTENDING BORE AROUND AND SPACED FROM SAID SHAFT, SPACED APART MEANS SEALING THE ENDS OF SAID BORE, A CONDUIT EXTERNAL OF SAID HOUSING AND HAVING ITS OPPOSITE ENDS IN SPACED APART COMMUNICATION WITH SAID BORE, AND A SECONDARY IMPELLER CARRIED BY SAID SHAFT IN SAID BORE FOR CIRCULATING FLUID THRU SAID CONDUIT TO THE OPPOSITE ENDS OF SAID BORE AS SAID SHAFT MOVES AXIALLY.

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